When people suffer from some types of heart arrhythmias, the result may be that blood flow to various parts of the body is reduced. Some arrhythmias may even result in a Sudden Cardiac Arrest (SCA). SCA can lead to death very quickly, e.g. within 10 minutes, unless treated in the interim.
Some people have an increased risk of SCA. People at a higher risk include individuals who have had a heart attack, or a prior SCA episode. A frequent recommendation is for these people to receive an Implantable Cardioverter Defibrillator (“ICD”). The ICD is surgically implanted in the chest, and continuously monitors the person's electrocardiogram (“ECG”). If certain types of heart arrhythmias are detected, then the ICD delivers an electric shock through the heart.
After being identified as having an increased risk of an SCA, and before receiving an ICD, these people are sometimes given a wearable cardiac defibrillator (“WCD”) system. A WCD system typically includes a harness, vest, or other garment for wearing by the patient. The system includes a defibrillator and external electrodes, which are attached on the inside of the harness, vest, or other garment. When a patient wears a WCD system, the external electrodes may then make good electrical contact with the patient's skin, and therefore can help monitor the patient's ECG. If a shockable heart arrhythmia is detected, then the defibrillator of the WCD system delivers the appropriate electric shock through the patient's body, and thus through the heart.
A wearable defibrillator system (WCD) system will typically be worn under the outer garments of a patient. If the patient collapses, a bystander might not help; even if they mean to help, they might not know about WCD systems, or what to do. A bystander trained in Cardio Pulmonary Resuscitations (CPR) might know to try to administer CPR chest compressions and ventilations; this intended rescuer, however, might not know that the patient is already wearing a WCD system, which could be further preparing to administer an electric shock through the patient, and which could be dangerous to whoever is touching the patient at the time.